With rapid advance of technology, modern robots of various varieties have finding their way of taking up more and more tasks ordinarily ascribed to humans, that they can be seen working in families for household cleaning, or working in factories for lifting/moving heavy objects, or even they can be seen playing important roles in outer space exploring.
Conventionally, in order to keep a mobile robot operational, it must return to a changer for charging before its power is running out. Please refer to FIG. 1, which is a functional block diagram of a conventional charging system for mobile robots. In FIG. 1, the charging system 1 is comprised of: a mobile robot 11; and a charger 12, including a charging control module 121 and an infrared emission module 122; wherein, the infrared emission module 122 is capable of issuing a plurality of infrared rays to be used by the mobile robot 11 as guidance for finding a path to the charger 12; and the charging control module 121 is used to specify and regulate the output power of the charger as well as the electrical characteristics thereof. By the aforesaid charging system 1, the path finding and guidance of the mobile robot 11 can be described as following: as the mobile robot 11 is operating in a area covered by the plural infrared rays of the infrared emission module 122 and when the power of the battery module 11 is dropping lower than a predefined value and is detected by the battery capacity inspection module 111, the battery capacity inspection module 111 will issue a signal to the control module 113 for directing the same to orientate and calibrate the position of the mobile robot 11 with respect to the direction of the infrared rays received by the infrared reception module 114, and thereby controlling the mobile module 115 to move the mobile robot 11 toward the charger 12 for charging. However, if there is an obstacle between the charger 12 and the mobile robot 11 that blocks the infrared rays to be received by the infrared reception module 114, the mobile robot 11 will have difficulty in finding the exact location of the charger 12 and thus a more complicated guidance design for overcoming such difficulty will be required.
Another conventional path finding and guidance method of mobile robot is achieved by the use of the calculation of encoders, arranged on the wheels of a mobile robot, to obtain the location of the mobile robot, However, as the slipping and idle spinning of the wheels might introduce error into the calculation, misguidance is a commonplace.
In yet another conventional path finding and guidance method of mobile robot, a plural reflective plates of the same shape are arranged on walls of an operation area of a mobile robot while being spaced from each other by the same interval, such that the mobile robot can use CCD cameras embedded therein to recognize the relative positioning of the plural reflective plates and thus evaluate the distance between itself and a charger accordingly. However, if the illumination of the operation area is changed or some other objects of the shape similar to that of the reflective plate are misidentified as the reflective plates, the distance can be erroneous. In addition, if the operation area is too bright or to dark, the CCD cameras might not be able to recognize those reflective plates that cause the guidance of the mobile robot impossible to be achieved. Moreover, since CCD cameras are required in the mobile robot, the manufacturing cost of the mobile robot is increased.
Therefore, it is in need of a path guidance method for an autonomous mobile device that is free from the aforesaid prior-art shortcomings.